1. Field of the Invention
This invention relates to, in general, methods for controlling the conductivity of polyimide and other polymer films, and more particularly, to methods for controlling the conductivity of polyimide and other polymer layers in electronic devices and to electronic devices using such layers.
2. Background Art
Organic polymer material layers are increasingly used in electronic devices. Polyimides, in particular, are of interest because of their favorable physical, chemical, and electrical properties, and the relative ease with which layers may be formed. Typical applications are, as an inter-layer insulating dielectric layer between different conductor layers, as a planarizing layer on uneven substrate surfaces to aid in smoothing out irregularities, as a masking layer, as a protective coating, or as a combination of the above where several functions may be performed by a single layer.
Ordinarily, polyimides are excellent insulating dielectrics. Volume resistivity is normally 10.sup.15 -10.sup..noteq. ohm-cm, dissipation factor is about 0.002 at 1 kHz, and dielectric strength in thin (1 .mu.m) layers is about 2.times.10.sup.8 volts per meter. Additionally, polyimides show excellent thermal stability compared to most other plastics. They are able to withstand exposure to temperatures of 400.degree.-450.degree. C. in air for periods of several hours without measureable thermal decomposition.
Because of the high resistivity and low dissipation, the prior art applications of polyimides have been limited to those occasions where it was desired to have an insulating dielectric layer, since there was no known method for controllably varying the conductivity of substantially pure polyimides. A method has been discovered by which this may be accomplished, in that a layer of a polymer, such as a polyimide, which is normally an insulating dielectric can be made partially conducting, and then if desired, returned to an insulating or any intermediate state. Additionally, in another embodiment of this invention, certain fabrication techniques of great utility for the production of electronic devices can be utilized with polyimide and other polymer materials to produce layers having significant conductivity or to produce layers which are substantially as non-conducting as the original polymer material, so that electrical leakage may be induced or eliminated as desired.
Accordingly, it is an object of this invention to provide an improved method for the fabrication of electronic devices having a polymer layer therein, particularly a polyimide layer, in contact with one or more conductor regions.
It is a further object of this invention to provide an improved method for controlling the conductivity of polymer layers, e.g. polyimides, in electronic devices and other applications.
It is an additional object of this invention to provide a method for inducing significant conductivity in polymer layers, by exposure of such layers to energetic particles.
It is a further object of this invention to control or eliminate the conductivity present in polymer layers, following exposure to energetic particles, by subsequent heating of the layers.
It is an additional object of this invention to control or eliminate the conductivity present in polymer layers, following exposure to energetic particles, by subsequent exposure of such layers to a gaseous plasma.
It is a further object of this invention to provide an improved method for the fabrication of conductor-insulating dielectric layer structures, on a substrate utilizing polymer dielectric layers.
It is an additional object of this invention to control or eliminate the intra- and inter-layer conductivity which occurs in conductor-insulating dielectric structures using polyimides where the conductor pattern has been etched or formed by means of bombardment with energetic particles.
It is a further object of the present invention to provide an improved method for the fabrication of electronic devices wherein the same material layer serves as an insulating dielectric in one region and a partially conducting dielectric, e.g. a resistor, in another region.
It is an additional object of this invention to provide an improved method for stabilizing the partially conductive behavior induced in polymer layers.
It is a still further object of this invention to provide improved electronic devices made by the above methods.